This application claims the priority of German Patent Application No. 198 22 031.6 filed May 15, 1998, which is incorporated herein by reference.
The invention relates to an auto-injection device. Such auto-injection devices are used for the administration of products, in particular medically or cosmetically effective fluids. For administration, an injection needle through which the product is dispensed is automatically inserted into a tissue by a predetermined path length after having been triggered by a drive mechanism.
Auto-injection devices typically comprise a housing, a container shiftably or moveably accommodated by the housing from which a product to be administered is dispensed through a needle arranged at an outlet of the container by advancing a piston, and a driven member of a drive unit, the driven member being shiftably accommodated by the housing. During auto-injection, the driven member advances the container in relation to the housing in the forward direction to a predetermined frontal position for inserting the needle, and the driven member advances the piston within the container for dispensing the product. When the container has reached its frontal position during an auto-injection, the needle has been advanced by a predetermined path length with respect to the container. The path length may also determine the penetration depth of the needle.
Auto-injection devices of the described design are known from U.S. Pat. Nos. 5,514,097; 159,192; and 5,643,214; as well as European Patent No. 0 516 473 B1. In the known auto-injection devices, the container is advanced together with the attached needle by a pressure which the driven member exerts on the piston.
It is an object of the invention to provide an auto-injection device ensuring that a product to be administered is only dispensed upon an injection needle having been completely advanced when being inserted into a tissue.
In one embodiment, the present invention provides an injection device comprising a housing, a container shiftably accommodated by said housing, carrying a needle and accommodating a moveable piston, and a drive unit comprising a driven member shiftably accommodated by said housing wherein, during an injection, the driven member is adapted for inserting said needle and advancing said container to a predetermined position in relation to said housing, at which said predetermined position said driven member is decoupled from said container and coupled with said piston for moving said piston within said container.
In one embodiment, an auto-injection device for administering a product in accordance with the present invention comprises at least a housing, a container shiftably accommodated by said housing and a driven member of a drive unit. The product is dispensed from the container through a needle at an outlet of the container by advancing a piston arranged in the container. The driven member is shiftably accommodated by the housing. During an auto-injection for inserting the needle, the driven member advances the container to a predetermined frontal position in relation to the housing and advances the piston within the container for dispensing all or part of the product. The driven member is not coupled with the piston until the frontal position of the container is reached. Upon reaching the frontal position of the container, it is decoupled from the container and coupled with the piston for advancing the piston within the container.
Accordingly, advancement of the container for inserting the needle is not effected by the piston, i.e., during this phase of movement there is no drive connection between the driven member and the piston. This rules out the possibility that the product may be dispensed prematurely during advancement of the container by even a small forward movement of the piston within the container, i.e., in relation to the container. By disengaging, i.e., decoupling, the driven member from the container and engaging it, i.e., coupling it, with the piston not earlier when the container is in its frontal position, the piston will only be advanced within the container upon the needle being inserted into the tissue to the required depth. The separation of the advancement of the container and the advancement of the piston within the container at the side of a drive mechanism increases dosing accuracy, due to pressure on the piston not being applied during advancement of the container, thus preventing the product from being dispensed prematurely.
The driven member may act directly on the container for advancement of the container.
In one embodiment, a transfer member is provided, which is driven along by the driven member during forward advancement, thus acting on the container and/or the container holder and resulting in advancement of the container. The transfer member may also be a container holder, but may be designed as a part separate therefrom.
The disengageable coupling may exist between the driven member and the transfer member. After disengaging the coupling in the frontal position of the container, a further advancement of the driven member, i.e., for advancement of the piston, does not result in any further advancement of the transfer member. The driven member now may be disengaged from the transfer member with respect to its own forward movement. It only pushes against the piston and drives the piston forward in the container. In one embodiment, the transfer member is accommodated by the housing shiftably in and against the direction of advancement of the piston.
In one embodiment, the driven member and the container are coupled to each other by a purely positive locking. In another embodiment, the coupling includes a non-positively locked connection between the driven member and the container. Hybrid locking connections may also be used.
A positively locked connection of the driven member and the transfer member may be formed by the driven member being connected to a first coupling means and the transfer member being connected to a second coupling means, with these two coupling means together forming a bolt-and-lock connection which is released at that point in time at which the container reaches its frontal position. The first coupling means may be rigidly connected to the driven member and effecting an advancement of the transfer member by pushing against a stop face of the transfer member. In one embodiment, the first coupling means is simply a cam projecting from the driven member. In the course of unlocking and the ensuing decoupling of the driven member from the transfer member, the cam, acting like a blocking bolt, is brought into coverage with a recess ending in the stop face, with the cam no longer pushing against the stop face and, so-to-speak, opening the lock by falling into the lock. The driven member is released from the transfer member, thus also releasing the coupling with the container, enabling the driven member to move further forward, in relation to the transfer member. In the course of this movement in relation to the transfer member, the driven member comes into pushing contact against the piston, thus effecting coupling of the driven member with the piston. The blocking bolt could also be connected to the transfer member and the lock to the driven member.
The decoupling of the driven member from the transfer member is may be effected by rotation of one of the two members in relation to the other. This relative rotation may be effected around a rotational axis parallel to the shift direction. The relative rotation is generated compulsorily due to advancement, in one embodiment by a coulisse guiding formed between the member to be rotated and the housing. Although a frictional force generated during the rotation may be used for selectively affecting the forward speed of the driven member and the transfer member, the coupling as such, i.e., blocking and releasing, is purely a positive locking effect.
In another embodiment, a combined positive and non-positive locking connection is used for coupling and decoupling the driven member with and from the container and with and from the piston. In this embodiment, the coupling may be formed between the driven member and a transfer member, although coupling directly with the container would also be possible.
The coupling may, in one embodiment, be formed by a snap coupling. During advancement of the driven member, a snapper (which also may be referred to as a snapper or snap member) pushes against a contact pressure surface, thus advancing the container. When the container has reached its frontal position, in which it is positioned against a stop in relation to the housing, the snap coupling is released by the drive force continuing to be exerted to the driven member. The driven member is then coupled to the piston and advanced further, free from the container and/or free from a transfer member. A slight supporting push upon reaching the frontal position of the container may certainly be desirable.
One or more of the means forming the coupling may be flexible made from products such as elastic. One or more snappers may be directly formed on the driven member, which is pushing therewith against a stop face on the container or the transfer member, should this be used. Such snappers may also be provided on the transfer member.
A third coupling means may also be used to provide the coupling. The third coupling may be flexible, such as a flexible elastic. The third coupling means may also be a flexible washer, in particular a spring washer, clamped between two opposite faces, one of the driven member, and the other of the transfer member, and being pushed over one of these two contact pressure surfaces as soon as the container has reached its frontal position.
The invention may also be advantageously used in such auto-injection devices in which the container is formed by a so-called multi-chamber ampoule. With these multi-chamber ampoules, the product to be administered is obtained only upon assembling the device by mixing the contents of several chambers which are separate from each other. Each of the chambers arranged in line is closed at its rear by a piston shiftably accommodated within the container. For mixing, a mixing member is pushed against the rear piston and pushes, in the course of its advancement within the container, each of the pistons forward to the most frontal piston. During advancement, a connection is made to each respective adjacent frontal chamber, thus displacing the content of each rear chamber to the respective adjacent chamber in front of it.
According to the invention, the mixing member, which may be a mixing tube, also forms the transfer member for advancement of the container. According to the invention, the mixing member has been allocated a dual function. From a design point of view, this may be achieved by the mixing member comprising a web radially extending outwards, preferably having the shape of a circumferential shoulder, for pushing against the rear face of the container or, if preferred, against a rear contact pressure surface of the container holder, the container holder in its forward movement being forced by the mixing member to take the container along with it. The frontal position of the container may be defined by the container holder striking the housing.
The housing may enclose both the container and the entire drive unit and may have the shape of a sleeve. In its most general design, however, the housing serves as a base section only, in relation to which displacement of the container and displacement of the driven member of the drive unit is effected and must therefore not exclusively be seen as a surrounding housing, although such an embodiment is possible.
Other features and advantages of the injection devices and methods of the present invention will become more fully apparent and understood with reference to the following description and appended drawings and claims.